1. Field of Invention
The present invention relates to illumination devices using organic electro-luminescence elements (hereinafter, xe2x80x9celectro-luminescencexe2x80x9d is referred to as xe2x80x9cELxe2x80x9d).
2. Description of Related Art
An organic EL device is a self-luminescent device wherein at least one organic luminescent layer is sandwiched by a cathode and an anode, which can be driven by a direct current voltage of approximately 3 volts and emit various colored lights. The organic EL device has many advantages as a display device, such as a high response speed and a large visual field angle, compared with a liquid crystal display device. Therefore, various practical applications of the organic EL device have been investigated, such as usage as a pixel for a display and as a light source.
Hitherto, in the organic EL device having such characteristics, a metallic thin film having a specular surface and being non-light-transmissible has been generally used as a cathode. In J. Appl. Phys., 86, 4067 (1999), an organic EL device is described in which a transparent cathode is used and a plurality of colored lights are emitted from both surfaces of a substrate.
However, in the above known technology, a structure, in which organic EL devices for individually emitting colored lights are laminated on each other, is used for emitting a plurality of colored lights, a problem has been found in that time and labor for manufacturing the structure are required. Further, it is practically difficult to prepare environment for manufacturing such a structure. Moreover, the assortment of solvents or the like is difficult to perform when a high-polymeric material is coated in a wet process such as spin coating instead of coating a low-molecular material by vapor deposition.
Accordingly, an object of the present invention is to provide a transparent organic EL device by forming organic EL devices on both surfaces of a substrate, each organic EL device being provided with at least one organic layer having a light-emitting function and being sandwiched by a transparent anode and cathode, whereby the organic EL device can display and illuminate in a plurality of colors.
An organic EL device in accordance with the invention includes an organic EL device formed on a light-transmissible and light-conductive substrate, the organic EL device including an anode, at least one organic layer having a light-emitting function, and a cathode, a first organic EL device being formed on a first surface of the substrate, the first organic EL device including the transparent anode and cathode, and a second organic EL device being formed on a second surface positioned opposite to the first surface of the substrate, the second organic EL device including the transparent anode and cathode.
With the above arrangement, an organic EL device which can display and illuminate in at least two colors can be provided.
The first organic EL element can be formed on the overall first surface of the substrate, and the second organic EL device can be formed on the overall second surface of the substrate.
With the above arrangement, an organic EL device which can display and illuminate in at least two colors can be provided.
The first organic EL element can be patterned on the first surface of the substrate so as to enable data display, and the second organic EL device can be formed on the overall second surface of the substrate.
With the above arrangement, an organic EL device which can display and illuminate in at least two colors can be provided.
The first and the second organic EL elements can be patterned on the first and the second surfaces, respectively, of the substrate so as to enable data display.
With the above arrangement, an organic EL device can be provided, which enables more complex data display by performing display and illumination in at least two colors and forming a pattern on each surface of the substrate which differs from the other.
The first and the second EL elements can individually emit colored lights differing from each other.
With the above arrangement, an organic EL device which can display and illuminate in at least two colors can be provided.